The present invention relates to a chucking mechanism for holding a disc recording medium having a central circular hole, such as a compact disc (CD) or a digital versatile disc (DVD), on the disc supporting surface of the turntable of a disc drive, and a disc drive incorporating such a chucking mechanism.
CDs and DVDs are removable disc recording mediums for use on the turntable of a disc drive, and have central circular holes for mounting themselves in the disc drive. The disc drive has a turntable having a disc supporting surface and a holding mechanism for holding a loaded disc recording medium on the disc supporting surface.
Of disc drives compatible with CDs and DVDs, portable CD players and DVD players and disc drives for use in notebook personal computers are required to be of a low profile. Many efforts are made to reduce the thickness of those disc drives even by a fraction of 1 mm. Primary factors responsible for determining the thickness of disc drives are the thickness of a drive motor for rotating a disc recording medium and the thickness of a holding mechanism for holding a disc recording medium on the turntable.
Various types of holding mechanisms are available in the art. The holding mechanism of the type which is most desirable from the standpoint of a low-profile design includes a chucking mechanism combined with a turntable and having movable teeth for pressing and holding a disc recording medium against the disc supporting surface of the turntable. FIGS. 6 to 8 of the accompanying drawings show a conventional chucking mechanism of the above type.
As shown in FIG. 6, a turntable 62 is connected to the output shaft of a flat disc-shaped spindle motor 60. A central block 64 for fitting in a central circular hole defined in a disc recording medium such as a CD or the like is disposed centrally on the upper surface of the turntable 62. The central block 64 is shaped as a flat disc-shaped cap-like member, and is fixed to the turntable 62 concentrically with the rotational axis of the turntable 62. The central block 64 has an outside diameter which matches the inner diameter of a central circular hole 14 (see FIG. 8) of a disc recording medium 16. The disc recording medium 16 to be mounted is positioned in alignment with the rotational axis of the turntable 62 by the central block 64. The turntable 62 has three engaging teeth 66 which are movable substantially radially into and out of the outer circumferential surface of the central block 64.
FIG. 7 shows in perspective the reverse side of the central block 64 illustrated in FIG. 6, illustrating internal components in the central block 64. The central block 64 has three sliders 68 supported thereon for radial sliding movement and normally urged to move radially outwardly by respective helical springs 70. The engaging teeth 66 are mounted on the respective radially outer ends of the sliders 68. When the sliders 68 slide radially, the engaging teeth 66 move radially into and out of the outer circumferential surface of the central block 64.
FIG. 8 shows at an enlarged scale each of the engaging teeth 66 illustrated in FIGS. 6 and 7. As shown in FIG. 8, the engaging tooth 66 has on its distal end a first engaging surface 72 facing obliquely upwardly and a second engaging surface 74 facing obliquely downwardly. For mounting the disc recording medium 16 on the turntable 62, the user holds the disc recording medium 16 by hand, and presses the disc recording medium 16 against the turntable 62 so that the central block 64 of the turntable 62 fits in the central circular hole 14 of the disc recording medium 16. The edge of the central circular hole 14 at the lower surface of the disc recording medium 16 engages and presses the first engaging surfaces 72 of the engaging teeth 66 downwardly. Therefore, when the user presses the disc recording medium 16 downwardly, the engaging teeth 66 are forced radially inwardly against the bias of the helical springs 70.
As the user continuously presses the disc recording medium 16 downwardly until the lower surface of the disc recording medium 16 abuts against the upper surface of the turntable 62, the pointed edges of the distal ends of the engaging teeth 66 are displaced upwardly from the central circular hole 14 of the disc recording medium 16. The second engaging surfaces 74 of the engaging teeth 66 are now brought into engagement with the edge of the central circular hole 14 at the upper surface of the disc recording medium 16, whereupon the engaging teeth 66 hold the disc recording medium 16 on the turntable 62. The position of the parts at this time is illustrated in FIG. 8. As can be seen from FIG. 8, the thickness of the engaging teeth 66 is about three times the thickness of the disc recording medium 16 that is mounted. The thickness of the engaging teeth 66 is large because the first engaging surface 72 and the second engaging surface 74 are vertically juxtaposed. Therefore, the thickness of the conventional chucking mechanism cannot be made smaller than the thickness of the engaging teeth 66.
Another conventional chucking mechanism is disclosed in Japanese Patent Laid-Open No. 2000-182305, for example. However, the disclosed conventional chucking mechanism has a thickness greater than the above-mentioned conventional chucking mechanism.
The conventional chucking mechanism described above with reference to FIGS. 6 to 8 appears to be of a lowest profile among the conventional mechanisms for holding a removable disc recording medium on the disc supporting surface of a turntable. Nevertheless, the thickness of the conventional chucking mechanism needs to be about three times the thickness of the disc recording medium. Many devices which incorporate disc drives for playing back removable disc recording mediums, e.g., portable CD players and DVD players and disc drives for use in notebook personal computers, have their commercial values increased directly by a reduction of their thickness even by 1 mm. In view of this trend, there is apparently a strong demand for lower-profile chucking mechanisms.